Herbicidally active substituted phenoxycinnamic acid derivatives

ABSTRACT

Herbicidally active compounds of the formula ##STR1## in which R 1  represents a hydrogen or chlorine atom, 
     R 2  represents a hydrogen atom, a cyano group, an optionally substituted radical selected from alkyl, aryl, alkanoyl, benzoyl, alkoxycarbonyl, alkenoxycarbonyl, alkinoxycarbonyl, aralkoxycarbonyl and aryloxycarbonyl, or a radical of the general formula --COOM, 
     in which 
     M represents a hydrogen atom, one equivalent of an alkali metal ion or alkaline earth metal ion or optionally substituted ammonium, and 
     R 3  represents a cyano group or a radical of the general formula ##STR2##  wherein Y represents an oxygen or sulphur atom or an imino (NH) or alkylimino (N-alkyl) group, 
     R 4  and R 5  independently of each other represent a hydrogen atom or a methyl group, 
     n is 0 or 1 and 
     Z represents an optionally substituted radical.

The present invention relates to certain new substituted phenoxycinnamicacid derivatives, to a process for their production, and to their use asherbicides. The invention further releates to novel intermediateproducts for the preparation of these substituted phenoxycinnamic acidderivatives, and to several processes for the synthesis of theintermediate products.

It is known that certain substituted diphenyl ethers can be used forcombating weeds (see R. Wegler, Chemie der Pflanzenschutz- undSchadlingsbekampfungsmittel (Chemistry of Plant Protection Agents andPesticides), volume 5, pages 73 to 80, Springer-Verlag Berlin,Heidelberg, New York 1977).

The action of the compounds from the series of the diphenyl ethers whichwere previously known as herbicides is however unsatisfactory for manypurposes.

The present invention now provides, as new compounds, substitutedphenoxycinnamic acid derivatives of the general formula ##STR3## inwhich

R¹ represents a hydrogen or chlorine atom,

R² represents a hydrogen atom, a cyano group, an optionally substitutedradical selected from alkyl, aryl, alkanoyl, benzoyl, alkoxycarbonyl,alkenoxycarbonyl, alkinoxycarbonyl, aralkoxycarbonyl andaryloxycarbonyl, or a radical of the general formula --COOM,

in which

M represents a hydrogen atom, one equivalent of an alkali metal ion oralkaline earth metal ion or optionally substituted ammonium, and

R³ represents a cyano group or a radical of the general formula ##STR4##wherein

Y represents an oxygen or sulphur atom, or an imino (NH) or alkylimino(N-alkyl) group,

R⁴ and R⁵ independently of each other represent a hydrogen atom or amethyl group,

n is 0 or 1 and

Z represents an optionally substituted radical selected from alkyl,aralkyl, aryl, alkoxy, alkenoxy, alkinoxy, aralkoxy and aryloxy, orrepresents a radical of the general formula OM', in which M'independently of M, has any of the meanings given above for M, or

Z furthermore also represents the radical of the general formula##STR5## wherein

R⁶ and R⁷ independently of each other represent an optionallysubstituted radical selected from alkyl, cycloalkyl, alkenyl, alkinyl,aralkyl and aryl or, together with the N atom to which they are bonded,form an optionally substituted saturated or unsaturated, optionallybenzo-fused, monocyclic or bicyclic structure, which optionally contains1 to 3 additional N atoms or an oxygen atom or sulphur atom as heteroatom or atoms.

According to the present invention we further provide a process for theproduction of a compound of formula (I) of the present inventioncharacterized in that a substituted phenoxybenzaldehyde of the generalformula ##STR6## in which

R¹ has the abovementioned meaning, is reacted with a methylene compoundof the general formula ##STR7## in which

R² and R³ have the abovementioned meanings, if appropriate in thepresence of a catalyst and, if appropriate, in the presence of adiluent, and, if desired, the compound of the formula (I), which is thusformed, is converted into another compound of the formula (I) bymodifying the radicals R² and/or R³.

The novel phenoxycinnamic acid derivatives of the formula (I) of thepresent invention are distinguished by an excellent herbicidal activityand exhibit good selectivity in various crops such as soy beans, cornand cereals. In addition to their high activity against broad-leavedweeds, the compounds according to the invention also show a goodactivity against grasses, especially against species of millet;furthermore, when used after emergence, they exhibit plantgrowth-regulating, especially growth-inhibiting, properties and can beused, for example, as cotton defoliants.

Surprisingly, the phenoxycinnamic acid derivatives according to thepresent invention exhibit a substantially better herbicidal action thancompounds which are known from the prior art and which have an analogousstructure and the same type of action.

Preferred phenoxycinnamic acid derivatives according to the presentinvention are those in which

R¹ represents a hydrogen or chlorine atom,

R² represents a hydrogen atom, a cyano, C₁ to C₄ alkyl or acetylradical, an optionally C₁ to C₄ alkyl-, C₁ to C₄ alkoxy-, halogen-,cyano- and/or nitro-substituted phenyl or benzoyl radical, a (C₁ to C₄alkoxy)-carbonyl, (C₃ to C₅ alkenoxy)-carbonyl, (C₃ to C₅alkinoxy)-carbonyl, phenyl-(C₁ or C₂ alkoxy) carbonyl orphenoxy-carbonyl radical or a radical of the general formula COOM,

in which

M represents a hydrogen atom, a sodium or potassium cation, oneequivalent of a magnesium or calcium cation, or ammonium whichoptionally contains 1 to 4 alkyl radicals with 1 to 4 carbon atoms, ofwhich radicals 2 optionally jointly form a ring, and

R³ represents a cyano group or a radical of the general formula ##STR8##in which

Y represents a oxygen or sulphur atom or an imino (NH) or methylimino(NCH₃) group,

R⁴ and R⁵ independently of each other represent a hydrogen atom or amethyl group

n is 0 or 1 and

Z represents a C₁ to C₄ alkyl or phenyl-C₁ or C₂ alkyl radical, anoptionally C₁ to C₄ alkyl-,

C₁ to C₄ alkoxy-, halogen-, cyano- and/or nitro-substituted phenylradical, a C₁ to C₄ alkoxy, C₃ to C₅ alkenoxy, C₃ to C₅ alkinoxy,phenyl-C₁ or C₂ alkoxy or phenoxy radical or a radical of the generalformula OM', in which M', independently of M, has any of those meaningsgiven immediately above for M, or

Z furthermore represents the radical of the general formula ##STR9## inwhich

R⁶ represents a C₁ to C₅ alkyl, cyanoethyl, methoxyethyl, C₃ to C₅alkenyl, C₃ to C₅ alkinyl, C₃ to C₆ cycloalkyl or phenyl-C₁ or C₂ alkylradical and

R⁷ represents a C₁ to C₅ alkyl, cyanoethyl, methoxyethyl, C₃ to C₅alkenyl, C₃ to C₅ alkinyl, C₃ to C₆ cycloalkyl, phenyl-C₁ or C₂ alkyl orphenyl radical, which is optionally substituted by C₁ to C₄ alkyl, C₁ toC₄ alkoxy, halogen, trifluoromethyl, cyano and/or nitro,

or wherein

the radicals R⁶ and R⁷, together with the nitrogen atom to which theyare bonded, form an optionally methyl- and/or ethyl-substituted radicalselected from pyrrolidyl, piperidyl, morpholinyl, indolyl, indolinyl,perhydroindolyl, 1,2,3,4-tetrahydroquinolyl,1,2,3,4-tetrahydroisoquinolyl, perhydroquinolyl, perhydroisoquinolyl andperhydroazepinyl.

Particularly preferred compounds of the present invention are those inwhich

R¹ represents a hydrogen or chlorine atom,

R² represents a hydrogen atom, a cyano, C₁ to C₄ alkyl, acetyl or C₁ toC₄ alkoxycarbonyl radical and

R³ represents a cyano or (C₁ to C₄ alkoxy)-carbonyl radical or a radicalof the general formula --COOM

wherein

M represents a sodium or potassium cation or one equivalent of amagnesium or calcium cation.

If, in the process according to the invention,5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde and dimethylmalonate are used as starting materials, the course of the reaction canbe represented by the following equation: ##STR10##

The formula (II) provides a definition of the phenoxybenzaldehydes to beused as starting materials in the process according to the invention.

Examples which may be mentioned are5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde and5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde.

The phenoxybenzaldehydes of the formula (II) have not previously beendescribed in the literature.

Accordingly the present invention further provides, as new compounds thephenoxybenzaldehydes of the formula (II), as defined above.

The present invention also provides a process for the production of acompound of formula (II), characterized in that

(a) a phenoxybenzaldehyde-acylal of the general formula ##STR11## inwhich

R¹ represents a hydrogen or chlorine atom, is reacted with an aqueousalkali metal hydroxide solution (such as a sodium hydroxide solution) ifappropriate in the presence of an additional diluent, (such as methanol)and if appropriate at a temperature between 10° and 80° C., the mixturemay then be diluted with water and the crystalline product of theformula (II) isolated by filtration, or

(b) a phenoxybenzyl alcohol of the general formula ##STR12## in which

R¹ represents hydrogen or chlorine, is reacted with an oxidizing agent(such as nitric acid) in the presence of a diluent (such as water andnitromethane), generally at a temperature between 10° and 80° C., themixture may then be diluted with water, and the crystalline product ofthe formula (II) isolated by filtration.

As examples of the acylals of the formula (IV) to be employed inpreparation variant (a), there may be mentioned5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde-diacetacylaland5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde-diacetacylal.

The acylals of the formula (IV) have not previously been described inthe literature.

According to the present invention we therefore further provide, as newcompounds, the acylals of the formula (IV) as defined above.

The present invention further provides a process for the production ofan acylal of the formula (IV), characterized in that aphenoxybenzaldehyde of the general formula ##STR13## in which

R¹ represents a hydrogen or chlorine atom, is reacted with aceticanhydride, if appropriate in the presence of a diluent (such asmethylene chloride) generally at a temperature between 10° and 80° C.,nitric acid is then added generally at a temperature between -10° and+20° C., after completion of the reaction the mixture may be dilutedwith water, the non-aqueous diluent, where present, separated off ordistilled off, and the product of the formula (IV), obtained incrystalline form, isolated by filtration.

As examples of the phenoxybenzaldehydes of the formula (VI) there may bementioned 3-(2-chloro-4-trifluoromethyl-phenoxy)-benzaldehyde and3-(2,6-dichloro-4-trifluoromethyl-phenoxy)-benzaldehyde.

The phenoxybenzaldehydes of the formula (VI) have not previously beendescribed in the literature.

According to the present invention we therefore further provide, as newcompounds, phenoxybenzaldehydes of the formula (VI) as defined above.

The present invention also provides a process for the production of aphenoxybenzaldehyde of formula (VI) characterized in that3-hydroxy-benzaldehyde is reacted with 3,4-dichloro- or3,4,5-trichloro-benzotrifluoride in the presence of an acid-bindingagent (such as potassium methylate) and in the presence of a diluent(such as dimethylsulphoxide and toluene), generally at a temperaturebetween 50° and 120° C. Working up can be effected in accordance withcustomary methods, for example by distilling off the volatilecomponents, digesting the residue with toluene, filtering, washing theresidue and concentrating the filtrate. The residue thus obtainedessentially contains the product of the formula (VI), which can bepurified via its bisulphite adduct.

As examples of the phenoxybenzyl alcohols of the formula (V) to beemployed in reaction variant (b) for the preparation of the compounds ofthe formula (II), there may be mentioned5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzyl alcohol and5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzyl alcohol.

The phenoxybenzyl alcohols of the formula (V) have not previously beendescribed in the literature.

According to the present invention we therefore further provide, as newcompounds, phenoxybenzyl alcohols of formula (V), as defined above.

The present invention also provides a process for the production of aphenoxybenzyl alcohol of formula (V) characterized in that aphenoxybenzoic acid chloride of the general formula ##STR14## in which

R¹ represents a hydrogen or chlorine atome, is reacted with a hydridecomplex (such as sodium boranate) in the presence of a diluent (such asdiglycol dimethyl ether (diglyme)), generally at a temperature between-20° and +20° C.

Working up can be carried out in the usual manner, for example bydiluting the mixture with water, acidifying it, for example with aceticacid, and isolating the product of the formula (V), which is obtained ina crystalline form, by filtration.

As examples of the phenoxybenzoic acid chlorides of the formula (VII)there may be mentioned5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzoic acid chloride and5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrobenzoic acid chloride.

The phenoxybenzoic acid chlorides of the formula (VII) are known (seeDE-OS (German Published Specification) No. 2,950,401).

A compound of the formula (VII) is obtained when a phenoxybenzoic acidof the general formula ##STR15## in which

R¹ represents a hydrogen or chlorine atom, is reacted with achlorinating agent (such as thionyl chloride) if appropriate with use ofa catalyst (such as dimethylformamide) and, if appropriate, with use ofa diluent (such as 1,2-dichloroethane) at a temperature between 10° and100° C., and thereafter volatile components are distilled off underreduced pressure.

The phenoxybenzoic acids of the formula (VIII), namely5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitrobenzoic acid and5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitrobenzoic acid, arealready known (see U.S. Pat. No. 3,928,416).

Preferred methylene compounds of formula (III) also to be used asstarting materials in the process according to the invention for thepreparation of the phenoxycinnamic acid derivatives of the formula (I)are those in which R² and R³ represent those radicals which hav alreadybeen mentioned in connection with the description of the preferred andparticularly preferred compounds of the formula (I).

As examples of the compounds of the formula (III) there may be mentionedmalonic acid, its sodium potassium, calcium and magnesium salt, and itsmethyl ester, ethyl ester, n- and iso-propyl ester, n-, iso, sec.- andtert.-butyl ester, malonodinitrile, cyanoacetic acid, its sodium,potassium, calcium and magnesium salt and its methyl ester, ethyl ester,n- and iso-propyl ester, n-, iso-, sec.- and tert.-butyl ester, andacetoacetic acid methyl ester, ethyl ester, n- and iso-propyl ester andn-, iso-, sec.- and tert.-butyl ester.

The compounds of the formula (III) are known.

From a compound of the formula (I),

in which

R³ represents a carboxyl or alkoxycarbonyl radical, it is possible toprepare another compound of the formula (I),

in which

R³ represents the radical of the general formula ##STR16## in which

R⁴, R⁵, Y, Z and n have the abovementioned meanings,

where necessary after conversion to the corresponding carboxylic acidchloride, by reaction with a compound of the general formula ##STR17##in which

R⁴, R⁵, Y, Z and n have the abovementioned meanings,

in accordance with customary methods, if appropriate in the presence ofan acid-binding agent and, if appropriate, in the presence of a diluent.

As further possible ways of interconverting the compounds of the formula(I) formed by the process according to the invention there may bementioned:

(1) decarboxylation, which in general takes place in situ, withoutisolation of the corresponding primary products, if malonic acid orcyanoacetic acid is used as a starting material;

(2) salt formation, for example by reaction of the corresponding acidwith a basic alkali metal compound or alkaline earth metal compound; and

(3) esterification, for example by reaction of the corresponding acidwith an alcohol in the presence of a base (such as diazabicycloundecene)or by reaction with a suitable alkyl halide.

Details of the process for the preparation of the novel phenoxycinnamicacid derivatives of the formula (I) are given below. The process isgenerally carried out in the presence of a catalyst. Compounds which aresuitable for accelerating condensation reactions between aldehydes andactivated methylene compounds (aldol condensations) are used for thispurpose. Preferably, aliphatic, aromatic or heterocyclic amines (such astrimethylamine, triethylamine, pyrrolidine, piperidine, dimethylaniline,dimethylbenzylamine, diazabicyclooctane, diazabicyclononene,diazabicycloundecene and pyridine) are used, where appropriate as saltsof weak acids (such as of acetic acid). The catalysts also includeaminocarboxylic acids (such as β-alanine). Some of these catalysts, suchas pyridine, can also advantageously be used as diluents.

Virtually any of the inert organic solvents can be used as diluents.They include, in particular, aliphatic and aromatic, optionallyhalogenated, hydrocarbons (such as pentane, hexane, heptane,cyclohexane, petroleum ether, petrol, ligroin, benzene, toluene, xylene,methylene chloride, ethylene chloride, chloroform, carbon tetrachloride,chlorobenzene and o-dichlorobenzene), ethers (such as diethyl ether anddibutyl ether, glycol dimethyl ether and diglycol dimethyl ether,tetrahydrofuran and dioxane), ketones (such as acetone, methyl ethylketone, methyl isopropyl ketone and methyl isobutyl ketone), esters(such as methyl acetate and ethyl acetate), nitriles (such asacetonitrile and propionitrile), amides (such as dimethylformamide,dimethylacetamide and N-methylpyrrolidone) and also dimethylsulphoxide,tetramethylenesulphone and hexamethylphosphorotriamide.

The reaction temperature can be varied within a substantial range. Ingeneral, the reaction is carried out at a temperature between 0° and200° C., preferably between 20° and 150° C.

The process according to the invention is in general carried out undernormal pressure.

In carrying out the process according to the invention, between 0.9 and1.5 mol, preferably between 1.0 and 1.2 mol, of methylene compound ofthe formula (III) are employed per mol of phenoxybenzaldehyde of theformula (II).

To carry out the process according to the invention, the procedurefollowed in general is to bring the reactants of the formulae (II) and(III), as well as the catalyst and the diluent, together at roomtemperature and then to stir the mixture at an elevated temperature,preferably at between 50° and 120° C., until completion of the reaction.The water formed in the reaction is removed, where necessary, via awater separator.

Working up can be effected in accordance with customary methods. Wherethe products are crystalline at room temperature, they are obtained bydiluting the reaction mixture with water, acidifying, if necessary, andfiltering.

It is, however, also possible to work up the mixture, in the usual way,by diluting with water, shaking with a virtually water-immiscibleorganic solvent (such as toluene) separating off the organic phase,washing it with water and distilling off the organic solvent.

The active compounds according to the invention influence plant growthand can therefore be used as defoliants, desiccants, agents fordestroying broad-leaved plants, germination inhibitors and, especially,as weedkillers. By "weeds" in the broadest sense there are meant plantsgrowing in places where they are not desired.

Whether the compounds according to the invention act as total herbicidesor selective herbicides depends essentially on the amount used.

The active compounds according to the present invention may be used, forexample, to combat the following plants:

dicotyledon weeds of the genera Sinapis, Lepidium, Galium, Stellaria,Matricaria, Anthemis, Galinsoga, Chenopodium, Urtica, Senecio,Amaranthus, Portulaca, Xanthium, Convolvulus, Ipomoea, Polygonum,Sesbania, Ambrosia, Cirsium, Carduus, Sonchus, Rorippa, Rotala,Lindernia, Lamium, Veronica, Abutilon, Emex, Datura, Viola, Galeopsis,Papaver, Centaurea and Solanum; and monocotyledon weeds of the generaEchinochloa, Setaria, Panicum, Digitaria, Phleum, Poa, Festuca,Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum,Agropyron, Cynodon, Monochoria, Fimbristylis, Sagittaria, Eleocharis,Scirpus, Paspalum, Ischaemum, Sphenoclea, Dactyloctenium, Agrostis,Alopecurus and Apera.

The active compounds according to the present invention may be used, forexample, as selective herbicides in the following cultures:

dicotyledon cultures of the genera Gossypium, Glycine, Beta, Daucus,Phaseolus, Pisum, Solanum, Linum, Ipomoea, Vicia, Nicotiana,Lycopersicon, Arachis, Brassica, lactuca, Cucumis and Cucurbita; and

monocotyledon cultures of the genera Cryza, Zea, Triticum, Hordeum,Avena, Secale, Sorghum, Panicum, Saccharum, Ananas, Asparagus andAllium.

However, the use of the active compounds according to the invention isin no way restricted to these genera but also embraces other plants, inthe same way.

Depending on the concentrations, the compounds can be used for the totalcombating of weeds, for example on industrial terrain and railway tracksand on paths and squares with or without trees. Equally, the compoundscan be employed for combating weeds in perennial cultures, for exampleafforestations, decorative tree plantings, orchards, vineyards, citrusgroves, nut orchards, banana plantations, coffee plantations, teaplantations, rubber plantations, oil palm plantations, cacaoplantations, soft fruit plantings and hopfields, and for the selectivecombating of weeds in annual cultures.

The active compounds can be converted to the customary formulations,such as solutions, emulsions, wettable powders, suspensions, powders,dusting agents, pastes, soluble powders, granules, suspension-emulsionconcentrates, natural and synthetic materials impregnated with activecompound, and very fine capsules in polymeric substances.

These formulations may be produced in known manner, for example bymixing the active compounds with extenders, that is to say liquid orsolid diluents or carriers, optionally with the use of surface-activeagents, that is to say emulsifying agents and/or dispersing agentsand/or foam-forming agents. In the case of the use of water as anextender, organic solvents can, for example, also be used as auxiliarysolvents.

As liquid diluents or carriers, especially solvents, there are suitablein the main, aromatic hydrocarbons, such as xylene, toluene or alkylnaphthalenes, chlorinated aromatic or chlorinated aliphatichydrocarbons, such as chlorobenzenes, chloroethylenes or methylenechloride, aliphatic or alicyclic hydrocarbons, such as cyclohexane orparaffins, for example mineral oil fractions, alcohols, such as butanolor glycol as well as their ethers and esters, ketones, such as acetone,methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, orstrongly polar solvents, such as dimethylformamide anddimethylsulphoxide, as well as water.

As solid carriers there may be used ground natural minerals, such askaolins, clays, talc, chalk, quartz, attapulgite, montmorillonite ordiatomaceous earth, and ground synthetic minerals, such ashighly-dispersed silicic acid, alumina and silicates. As solid carriersfor granules there may be used crushed and fractionated natural rockssuch as calcite, marble, pumice, sepiolite and dolomite, as well assynthetic granules of inorganic and organic meals, and granules oforganic material such as sawdust, coconut shells, corn cobs and tobaccostalks.

As emulsifying and/or foam-forming agents there may be used non-ionicand anionic emulsifiers, such as polyoxyethylene-fatty acid esters,polyoxyethylene-fatty alcohol ethers, for example alkylaryl polyglycolethers, alkyl sulphonates, alkyl sulphates, aryl sulphonates as well asalbumin hydrolysis products. Dispersing agents include, for example,lignin sulphite waste liquors and methylcellulose.

Adhesives such as carboxymethylcellulose and natural and syntheticpolymers in the form of powders, granules or latices, such as gumarabic, polyvinyl alcohol and polyvinyl acetate, can be used in theformulations.

It is possible to use colorants such as inorganic pigments, for exampleiron oxide, titanium oxide and Prussian Blue, and organic dyestuffs,such as alizarin dyestuffs, azo dyestuffs or metal phthalocyaninedyestuffs, and trace nutrients, such as salts of iron, manganese, boron,copper, cobalt, molybdenum and zinc.

The formulations in general contain from 0.1 to 95 percent by weight ofactive compound, preferably from 0.5 to 90 percent by weight.

The active compounds which can be used according to the invention, assuch or in the form of their formulations, can also be employed, forcombating weeds, as mixtures with known herbicides, finishedformulations or tank mixing being possible. Mixtures with other knownactive compounds, such as fungicides, insecticides, acaricides,nematicides, bird repellents, growth factors, plant nutrients and agentswhich improve soil structure, are also possible.

The active compounds can be used as such, in the form of theirformulations or in the use forms prepared therefrom by further dilution,such as ready-to-use solutions, suspensions, emulsions, powders, pastesand granules. They are used in the customary manner, for example bywatering, spraying, atomizing or scattering.

The active compounds according to the invention can be applied eitherbefore or after emergence of the plants. They are preferably appliedbefore emergence of the plants, that is to say by the pre-emergencemethod. They can also be incorporated into the soil before sowing.

The amount of active compound used can vary within a substantial range.It depends essentially on the nature of the desired effect. In general,the amounts used are between 0.05 and 10 kg of active compound per ha,preferably between 0.1 to 5 kg/ha.

The active compounds according to the invention, when used afteremergence, exhibit growth-regulating properties.

The present invention also provides herbicidal compositions containingas active ingredient a compound of the present invention in admixturewith a solid diluent or carrier or in admixture with a liquid diluent orcarrier containing a surface-active agent.

The present invention also provides a method of combating weeds whichcomprises applying to the weeds, or to a habitat thereof, a compound ofthe present invention alone or in the form of a composition containingas active ingredient a compound of the present invention in admixturewith a diluent or carrier.

The present invention further provides crops protected from damage byweeds by being grown in areas in which immediately prior to and/orduring the time of the growing a compound of the present invention wasapplied alone or in admixture with a diluent or carrier.

It will be seen that the usual methods of providing a harvested crop maybe improved by the present invention.

PREPARATIVE EXAMPLES EXAMPLE 1 ##STR18##

270 g of 5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-benzaldehydeand 6 g of piperidine were added, at 25° C., to 89.5 g of malonic acidin 570 ml of pyridine. The reaction mixture was stirred for 5 hours at85° to 90° C. and was then heated for 90 minutes under reflux, afterwhich it was poured onto water, the mixture was acidified withhydrochloric acid and the product was filtered off. The crystallineproduct was recrystallized from n-butanol. 200 g (66% of theory) of3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoicacid, of melting point 192° C., were obtained in the form of yellowcrystals.

The compounds of the formula (I) listed in the examples which followwere also prepared in accordance with the method described in Example 1:

EXAMPLE 2 ##STR19## Melting point: 120° C. EXAMPLE 3

Using cyanoacetic acid: ##STR20## Melting point: 142° C.

EXAMPLE 4 ##STR21##

19 g of 5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-benzaldehyde,5.7 g of ethyl cyanoacetate, 0.6 g of acetic acid, 0.3 g of piperidineand 120 ml of toluene were mixed and heated to the boil for 6 hoursunder a water separator. 200 ml of toluene was then added and theorganic phase was washed with water. The solvent was distilled from theorganic phase and the residue was caused to crystallise by digestionwith methanol. 12.5 g (53% of theory) of ethyl2-cyano-3-(5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-phenyl)-propenoate,of melting point 99° C., were obtained in the form of pale yellowcrystals.

The compounds of the formula (I) listed in the examples which followwere also prepared in accordance with the method described in Example 4:

EXAMPLE 5

Using malodinitrile: ##STR22## Melting point: 114° C.

EXAMPLE 6

Using methyl cyanoacetate: ##STR23## Melting point: 148° C.

EXAMPLE 7

Again using methyl cyanoacetate but with another aldehyde: ##STR24##Highly viscous oil

EXAMPLE 8 ##STR25##

2.2 g of3-(5-(2-chloro-4-trifluoromethylphenoxy)-2-nitro-phenyl)-propenoic acid(compound (2)) were stirred with 50 ml of methanol and 0.31 g of sodiummethylate until a solution was formed; the solvent was then distilledoff. 1.95 g (84% of theory) of sodium3-(5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-phenyl)-propenoate,melting with decomposition at 230°-240° C., were obtained as theresidue.

EXAMPLE 9 ##STR26##

42.2 g of3-(5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-phenyl)-propenoicacid (compound (1)) were introduced into 120 ml of acetone and 18.7 g ofdiazabicycloundecene (DBU) were added, at 20° C. After 30 minutes, 35 gof methyl iodide were added dropwise. The reaction mixture was stirredfor 15 hours at 50° to 60° C. and was diluted with water and methylenechloride; the organic phase was extracted by shaking with dilute sodiumhydroxide solution and then with dilute hydrochloric acid, and waswashed with water, dried and filtered. The solvent was distilled off thefiltrate, and the residue was digested with ligroin and filtered off.

20.5 g (47% of theory) of methyl3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-phenyl)-propenoate,of melting point 90° C., were obtained.

The compounds of the formula (I) listed in the examples which followwere also prepared in accordance with the method described in Example 9:

EXAMPLE 10

Using 2-iodopropane: ##STR27## Melting point: 102° C.

EXAMPLE 11

Using ethyl iodide ##STR28## Melting point: 86° C.

PREPARATION OF STARTING MATERIALS EXAMPLE 12 ##STR29## Process variant(a):

A mixture of 12.1 g of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde-diacetacylal,40 ml of methanol, 30 ml of water and 7 ml of 4% strength aqueous sodiumhydroxide solution was stirred for 90 minutes at 40° C. and was thenpoured into water, and the product was filtered off. 9.0 g (95% oftheory) of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde, ofmelting point 115° C., were obtained.

EXAMPLE 13 ##STR30## Process variant (b):

100 g of 5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitrobenzyl alcoholwere dissolved in 370 ml of nitromethane. A mixture of 86.4 g of 65%strength nitric acid and 43.2 g of water was then added dropwise in thecourse of 90 minutes to this solution, at 60° to 65° C., and the mixturewas stirred for 8 hours at 60° to 65° C. It was then diluted with 4liters of water, and the product was filtered off. 50.2 g (50% oftheory) of 5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde,of melting point 95° C., were obtained.

EXAMPLE 14 ##STR31##

34 g of 3-(2,6-dichloro-4-trifluoromethyl-phenoxy)-benzaldehyde and 42.8g of acetic anhydride were dissolved in 100 ml of methylene chloride andthe solution was stirred for 1 hour at 40° C. When it had cooled to 20°C., 2 g of sulphuric acid were added. 10 g of 70% strength nitric acidwere then added dropwise at 2° to 5° C. and the reaction mixture wasstirred for 4 hours at 0° to 5° C. For working up, 1 liter of water wasadded, the methylene chloride was distilled off and the crystallineproduct was filtered off. 80 g of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzaldehyde-diacetacylal,of melting point 132° C., were obtained.

EXAMPLE 15 ##STR32##

A solution of 41.5 g of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzoic acid chloridein 100 ml of diglyme was added to a mixture of 4.2 g of sodium boranateand 60 ml of diglyme at -5° to -10° C. The reaction mixture was stirredfor about 15 hours at room temperature, diluted with 1.2 liters of waterand acidified with acetic acid, and the product was filtered off. 36 g(94% of theory) of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzyl alcohol, ofmelting point 143° C., were obtained.

The compound shown in the example which follows was also prepared inaccordance with the method described in Example 15:

EXAMPLE 16 ##STR33## Melting point 84° C. EXAMPLE 17 ##STR34##

A mixture of 123 g of potassium hydroxide, 122 g of3-hydroxy-benzaldehyde and 1 of methanol was stirred until a solutionformed. The methanol was then carefully distilled off in vacuo. Theresidue was dissolved in 1.8 liters of dimethylsulphoxide. 300 ml oftoluene were added and slowly distilled off again. At the same time, 536g of 3,4,5-trichloro-benzotrifluoride were added dropwise. The reactionmixture was then stirred for 9 hours at 90° to 95° C. Thereafter thesolvent was distilled off in vacuo and the residue was stirred with 1.2liters of toluene and filtered off. The filtrate was washed with alkaliand then until neutral, and was concentrated. 430 g (64% of theory) of3-(2,6-dichloro-4-trifluoro-methylphenoxy)-benzaldehyde, of meltingpoint 54° C., were obtained.

EXAMPLE 18 ##STR35##

79.2 g of 5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzoicacid and 0.5 ml of dimethylformamide were introduced into 150 ml of1,2-dichloro-ethane. 28.6 g of thionyl chloride were added dropwise at60° to 65° C. and the mixture was heated under reflux for 1 hour. Thesolution was clarified with active charcoal and filtered throughkieselguhr. The mother liquor was concentrated and the residue wasrecrystallized from cyclohexane. 65.1 g (79% of theory) of5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitro-benzoic acidchloride, of melting point 95° C., were obtained.

The compound shown in the example which follows was also prepared inaccordance with the method described in Example 18.

EXAMPLE 19 ##STR36## Melting point 61° C.

The herbicidal activity of the compounds of this invention isillustrated by the following examples wherein the compounds according tothe present invention are each identified by the number (given inbrackets) of the corresponding preparative example.

EXAMPLE 20

Pre-emergence test

Solvent: 5 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weightof active compound was mixed with the stated amount of solvent, thestated amount of emulsifier was added and the concentrate was dilutedwith water to the desired concentration.

Seeds of the test plants were sown in normal soil and, after 24 hours,watered with the preparation of the active compound. It was expedient tokeep constant the amount of water per unit area. The concentration ofthe active compound in the preparation was of no importance, only theamount of active compound applied per unit area being decisive. Afterthree weeks, the degree of damage to the plants was rated in % damage incomparison to the development of the untreated control. The figuresdenoted:

0%=no action (like untreated control)

100%=total destruction

In this test, active compounds (1), (2) and (8) exhibited a very goodselective herbicidal activity.

EXAMPLE 21

Post-emergence test

Solvent: 5 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weightof active compound was mixed with the stated amount of solvent, thestated amount of emulsifier was added and the concentrate was dilutedwith water to the desired concentration.

Test plants which had a height of 5 to 15 cm were sprayed with thepreparation of the active compound in such a way as to apply the amountsof active compound per unit area which were prescribed. Theconcentration of the spray liquor was so chosen that the particularamounts of active compound desired were applied in 2,000 liters ofwater/ha. After 3 weeks, the degree of damage to the plants was rated in% damage in comparison to the development of the untreated control. Thefigures denoted:

0%=no action (like untreated control)

100%=total destruction

In this test, active compounds (1), (2) and (8) exhibited a very goodherbicidal activity.

It will be understood that the specification and examples areillustrative but not limitative of the present invention and that otherembodiments within the spirit and scope of the invention will suggestthemselves to those skilled in the art.

We claim:
 1. A substituted phenoxycinnamic acid derivative of theformula ##STR37## in which R² represents a hydrogen atom, a cyano, C₁ toC₄ alkyl, acetyl or C₁ to C₄ alkoxycarbonyl radical and R³ represents acyano or (C₁ to C₄ alkoxy)-carbonyl radical or a radical of the generalformula --COOM wherein M represents a hydrogen, sodium or potassiumcation or one equivalent of a magnesium or calcium cation.
 2. A compoundaccording to claim 1, wherein such compound is3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoicacid of the formula ##STR38## or a salt thereof.
 3. A compound accordingto claim 1, wherein such compound is3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoicacid nitrile of the formula ##STR39##
 4. A compound according to claim1, wherein such compound is ethyl2-cyano-3-(5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-phenyl)-propenoateof the formula ##STR40##
 5. A compound according to claim 1, whereinsuch compound is ethyl3-(5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitrophenyl)-propenoateof the formula ##STR41##
 6. A herbicidal composition comprising asactive ingredient a herbicidally effective amount of a compoundaccording to claim 1 in admixture with a diluent.
 7. A method ofcombating weeds comprising applying to the weeds, or to a habitatthereof, a herbicidally effective amount of a compound according toclaim
 1. 8. The method according to claim 7, wherein such compoundis3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoicacid nitrile, ethyl2-cyano-3-(5-(2,6-dichloro-4-trifluoromethylphenoxy)-2-nitro-phenyl)-propenoate,or3-(5-(2,6-dichloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoicacid or3-(5-(2-chloro-4-trifluoromethyl-phenoxy)-2-nitrophenyl)-propenoic acidor a salt thereof.